While pilots taxi their departing airplanes toward the runways they expect to use, they're also working their way through a lengthy series of preflight steps and checklists to make certain everything is properly set for takeoff.

In addition, the pilot may be giving the co-pilot a briefing on the departure plan (which way to turn, altitude to fly, etc), while fielding radio calls and listening to other aircraft on the field. And, as is often the case in an early morning departure at a smaller airport, a clearance to take off may be issued early by the control tower before the aircraft has reached the runway area.

The question has already been asked why the air traffic controller wasn't monitoring the flight after issuing the takeoff clearance, but the system has never required that, and controllers have many heads-down duties in the tower as well.

True, every year many sharp controllers catch human errors in progress in time to radio a quick warning (and there is a prestigious recognition called the Archie League Award for such heroics), but baby-sitting every pilot's level of compliance with every clearance just isn't possible.

And then there's the actual layout of the Lexington airport. When there's just one runway, or two runways crossing in the middle with the ends far apart, the opportunity to get mixed up is minimal. But when two different runways begin from nearly the same spot, the opportunity for confusion becomes possible.

That does not mean Lexington is somehow designed wrong or is unsafe, but it means there's an added potential for trouble.

At Lexington, the Comair crew was cleared to use the 7,000-foot runway that was long enough for a safe ground roll and liftoff. That's Runway 22 (add a zero and you have the magnetic compass heading, 220).